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Minimum current for zener diodes

Started by Sonnich Jensen May 12, 2011
Hi

What is the minimum current for a zener, such as BZX55/C5V6 to work
properly?
I tried using 500uA, but it does not seem good. I looks like less than
1mA is not enough, more like 2mA.

Sonnich
On May 12, 5:14=A0am, Sonnich Jensen <sonnichjen...@gmail.com> wrote:
> Hi > > What is the minimum current for a zener, such as BZX55/C5V6 to work > properly? > I tried using 500uA, but it does not seem good. I looks like less than > 1mA is not enough, more like 2mA. > > Sonnich
most zeners need more than 50nA. 1 uA is plenty
On Thu, 12 May 2011 02:14:06 -0700 (PDT), Sonnich Jensen <sonnichjensen@gmail.com> wrote:

>Hi > >What is the minimum current for a zener, such as BZX55/C5V6 to work >properly?
It's in the datasheet, did you miss it?
>I tried using 500uA, but it does not seem good. I looks like less than >1mA is not enough, more like 2mA.
Bad zener? "not seem good" in what way? 500uA is enough, C5V6 should get between 5.2 to 6V according to one datasheet I looked at.
> >Sonnich
On May 12, 11:14=A0am, Sonnich Jensen <sonnichjen...@gmail.com> wrote:
> Hi > > What is the minimum current for a zener, such as BZX55/C5V6 to work > properly? > I tried using 500uA, but it does not seem good. I looks like less than > 1mA is not enough, more like 2mA.
It's an interesting question, and the answer is complicated and varies with the breakdown voltage. Low voltage "zener" diodes break down by the Zener mechanism, while at higher voltages, avalanche breakdown takes over http://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/breakdown/br= eakdown.html Your 5.6V diodes sit right on the border between the two mechanisms and both are likely to be active. Avalanche breakdown tends to be noisy at low currents - the actual areas in which the avalanches occurs tends to be tiny, so at "low" currents (less than a milliamp) there may be only one electron in transit at any one moment. The process by which this electron creates new charge carriers is statistical, and if that one electron doesn't succeed in generating at least one new charge carrier as as it makes its way across the junction, the current stops for a bit until thermal noise eventually promotes another charge carrier into the conduction band, giving you are rather jagged voltage-versus time curve. Search on "micro-plasmas" and note that glass-packaged zener diodes tend to behave different when exposed to light (and have been known to emit light when carrying current). The Zener mechanism seems to be quieter. There was a nice - tolerably long - thread on the subject - "Zener Diode Oscillation" - here back in 1997. Winfield Hill and the late Tony Williams posted a lot of interesting measurements and some interesting references from the semiconductor physics literature. -- Bill Sloman, Nijmegen
On Thu, 12 May 2011 02:14:06 -0700 (PDT), Sonnich Jensen
<sonnichjensen@gmail.com> wrote:

>Hi > >What is the minimum current for a zener, such as BZX55/C5V6 to work >properly? >I tried using 500uA, but it does not seem good. I looks like less than >1mA is not enough, more like 2mA. > >Sonnich
--- For a Zener to "work properly" the current through it should be as specified on the data sheet: http://www.rectron.com/data_sheets/bzx55c-bs.pdf -- JF
On May 12, 5:14=A0am, Sonnich Jensen <sonnichjen...@gmail.com> wrote:
> Hi > > What is the minimum current for a zener, such as BZX55/C5V6 to work > properly? > I tried using 500uA, but it does not seem good. I looks like less than > 1mA is not enough, more like 2mA. > > Sonnich
There's some nice graphs in the General Semi data sheet here. http://www.datasheetcatalog.com/datasheets_pdf/B/Z/X/5/BZX55-C5V6.shtml The low voltage zeners have really mushy corner's, the dynamic impedance is pretty poor if you just barely turn them 'on'. At 2mA it looks like the C5V6 is still in the corner of the I-V. You can run the higher voltage zeners at lower current... 'course as Bill point out they are noiser. Why do you want to run at the minimum current? George H.
On May 12, 9:36=A0am, George Herold <gher...@teachspin.com> wrote:
> On May 12, 5:14=A0am, Sonnich Jensen <sonnichjen...@gmail.com> wrote: > > > Hi > > > What is the minimum current for a zener, such as BZX55/C5V6 to work > > properly? > > I tried using 500uA, but it does not seem good. I looks like less than > > 1mA is not enough, more like 2mA. > > > Sonnich > > There's some nice graphs in the General Semi data sheet here.http://www.d=
atasheetcatalog.com/datasheets_pdf/B/Z/X/5/BZX55-C5V6.shtml
> > The low voltage zeners have really mushy corner's, the dynamic > impedance is pretty poor if you just barely turn them 'on'. > > At 2mA it looks like the C5V6 is still in the corner of the I-V. =A0You > can run the higher voltage zeners at lower current... 'course as Bill > point out they are noiser. =A0Why do you want to run at the minimum > current? > > George H.
5 milliamps is on the spec sheet

George Herold wrote:

> On May 12, 5:14 am, Sonnich Jensen <sonnichjen...@gmail.com> wrote: > >>Hi >> >>What is the minimum current for a zener, such as BZX55/C5V6 to work >>properly? >>I tried using 500uA, but it does not seem good. I looks like less than >>1mA is not enough, more like 2mA.
> > There's some nice graphs in the General Semi data sheet here. > http://www.datasheetcatalog.com/datasheets_pdf/B/Z/X/5/BZX55-C5V6.shtml > > The low voltage zeners have really mushy corner's, the dynamic > impedance is pretty poor if you just barely turn them 'on'.
The TempCo of Zeners depends on the current, too. No wonders, TempCo is minimal at the recommended current. TempCo is typically positive for lower currents and negative for higher currents. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Sonnich Jensen <sonnichjensen@gmail.com> wrote:

>Hi > >What is the minimum current for a zener, such as BZX55/C5V6 to work >properly? >I tried using 500uA, but it does not seem good. I looks like less than >1mA is not enough, more like 2mA.
In my experience you'll need at least several mA (say about 4mA) through a zener to get it operating at its specified voltage. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------
On Thu, 12 May 2011 16:27:43 GMT, nico@puntnl.niks (Nico Coesel)
wrote:

>Sonnich Jensen <sonnichjensen@gmail.com> wrote: > >>Hi >> >>What is the minimum current for a zener, such as BZX55/C5V6 to work >>properly? >>I tried using 500uA, but it does not seem good. I looks like less than >>1mA is not enough, more like 2mA. > >In my experience you'll need at least several mA (say about 4mA) >through a zener to get it operating at its specified voltage.
We seem to have a "random rattling" issue here. Did _anyone_ pay attention to Field's post showing that the I VALUE is specified on the data sheet? And ALL "zener's" have an Ohmic term. To get really steep slope you need to use an active device, such as a TL431. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Obama is not the solution, Obama is the problem!